The disclosure relates generally to electrostatic precipitator (ESP) cleaning, and more particularly, to a system and method for cleaning collecting plates of an ESP by applying a resonant frequency wave.
Electrostatic precipitators (ESP), or electrostatic air cleaners, are particulate collection machines that pull particles from a moving gas such as air using an electrostatic charge on or commingled with the particles causing them to move perpendicular to gas flow and come to rest on the collecting plates. In industrial settings, cleaning of ESP collecting plates is accomplished using mechanical force, applied by hitting or rapping the collecting plates using a drop rod or tumbling hammer, which dislodges particles from the collecting plate to a hopper. Specific to electromagnetic rappers, the operator varies the lift height of the plunger, the number of times the plunger strikes and how frequently the rapper strikes. However, there is limited effort to vary the force based on debris load or position within the fields. It is common to vary the lift height of an electromagnetic rapper based on its location within the electrostatic precipitator. However, the tumbling hammer systems can only vary the “on” and “off” time of the cycle.
With regard to the force applied, the mechanical force is typically introduced at a periphery of the collecting plate, e.g., the extreme top or bottom of the collecting plate. Consequently, the shock wave caused by that force dissipates as it travels through the collecting plate. To effectively clean the periphery of the collecting plate, it is necessary to impart excessive force to the components nearest the point of initial impact. The excessive force creates a number of problems such as fatigue failures or misalignment, and collected particle re-entrainment into the gas stream. Most attempts at improving the effectiveness of this cleaning approach relate to decreasing the number of collecting plates cleaned by a single hammer device. In this manner, the disparity between the force at the point of introduction to the periphery on the plate is reduced. However, the change increases the cost of the ESP and increases the number of housing openings required for the ESP.
Industrial ESPs use a number of stages or fields in an ESP to remove particles. However, over 85% of the particles are collected in the inlet field collecting plate(s). As a result, the particle layer on these collecting plates will build up quicker compared to subsequent fields. More particularly, at the inlet of the first field, the particles are typically evenly distributed in the vertical plane. As one progresses through the ESP, however, the particles tend to migrate downward increasing the particle density towards the bottom of the collecting plates. This condition results in a relatively even particle thickness from top to bottom at the inlet field collecting plates and a skewed thickness toward the bottom in the outlet field collecting plates. Current cleaning approaches do not address this anomaly.
Acoustic horns have been applied to remove particles from collecting plates.